What's the premium for a 3Br/3BA apt?

$925 or so.

It depends on the school district, actually. There is no real premium in areas with "bad" districts. A big one elswhere.

I was looking at this building 200 East 74th Street. The price/sq ft seems all over the place depending on the size of the apt.

http://streeteasy.com/nyc/building/200-east-74-street-new_york

See StreetEasy's Condo Listing snapshot, with its $-per-ft² ascending with size:

1,168 Studio
1,197 1
1,432 2
1,776 3
2,006 4+

You'll see the same pattern in any building, depending on location.

If you buy more than 1k share of apps. It'll cost IOU a 40% premium.

call a local broker who has done some transactions in the area, get some real comps. They are free, and you can get a few comps from a few different brokers who know the building and area. Whatever you do, dont listen to any advice on this board, your description is very general as are the responses and it all looks wrong to me.

Nwt, I disagree with you for a change. Usually larger apts tend be in a much better condition and in better buildings which skews the per sq ft price for se listing average. Also, even within the same new development, premium space tends be larger apts. I would say, apples to apples, the price difference is probably half what the streeteasy condo snapshot shows.

I wasn't looking for industry average, but rather price difference within the same building. I guess a large 3BR/3BA is rare compared to a large junior 4, so there could be a slight premium for the extra space. I've been looking at the current market price for junior 4 on the UES, they seem a bit low compared to larger size apartments in the same building.

15-20 percent assuming junior 4 has 1.5 bath is less than 850 sq ft, and can not be converted to 2 bed. If it is larger say 950 sq ft, and can be converted to 2 bed, 10 percent.